1. Field of the Invention
The present invention relates to an in-plane-switching liquid crystal display for large pixel type scarcely producing defects and easily repairing defects.
2. Description of the Related Art
Recently, because liquid crystal display has been utilized in thin type large screen television, liquid crystal displays are becoming large. For the purpose utilizing the liquid crystal display in the television, because many peoples may watch the same television simultaneously, the liquid crystal display must have wide viewing angle compared with the liquid crystal display of personal computer. The in-plane-switching liquid crystal display is one of wide viewing angle liquid crystal display.
The in-plane-switching liquid crystal display comprises an array substrate and a color filter substrate corresponding to the array substrate. There is a distance between the array substrate and the color filter substrate. Besides, liquid crystal molecules fill between the array substrate and the color filter substrate. FIG. 6 shows a conventional array substrate 60 of in-plane-switching liquid crystal display. The array substrate 60 is manufactured according to the following steps (1) to (8). (1) A transparent insulated substrate (glass substrate, etc., is provided. (2) Gate lines 62 and Cs (storage capacity) lines 64 are formed on the glass substrate. (3) A first insulated layer is formed by CVD (chemical vapor deposition) method. (4) TFTs (Thin film transistors) 66, signal lines 68, pads 70 and pixel lines 72 are formed on the same layer. The gate electrodes of TFT 66 are a portion of the gate line. The drain electrodes of TFT 66 are connected to the signal lines 68. The pads 70 are corresponding to the Cs lines 64, and the insulated layer is between the pads 70 and the Cs lines 64. The pixel lines 72 are used to connect the pads 70 and the source electrodes. (5) A second insulated layer is formed on the TFT 66, signal lines 68, pads 70 and pixel lines 72. (6) Through holes 74 are formed on the second insulated layer and disposed above the corresponding position of the pads 70. (7) Pixel electrodes 76 and common electrodes 78 are formed. (8) An alignment layer is formed on the pixel electrodes 76 and the common electrodes 78.
The pixel electrodes 76 connect to the pads 70 via the through hole 74, and are of stripe shape in the pixel. The number of the pixel electrodes is arbitrary. The common electrodes 78 are of a strip shape, and are formed on the same layer of the pixel electrodes 76. The pixel electrodes 76 are parallel to the common electrodes 78. The pixel electrodes 76 and the common electrodes 78 induce electric field parallel to the glass substrate, and the intensity of the electric field affect the alignment of the liquid crystal molecules.
Furthermore, the common electrodes 78 are also formed on the peripheral area of the pixel, and a portion of the common electrodes 78 overlap the signal lines 68 so that the common electrodes 78 can shield the electric field inducing by the signal lines 68 to prevent the malfunction of liquid crystal molecules. On the inside area of the pixel, the common electrodes 78 that are corresponding to the pixel electrodes 76 do not overlap the signal lines 68 and disconnected in the middle of the pixel.
The resolution of the television is fixed. Therefore, when the liquid crystal display is utilized in the television, the liquid crystal display must match the television. That is, when televisions are becoming large and liquid crystal displays are also becoming large, each pixel is becoming large at the fixed number of pixels.
The distance between the pixel electrodes 76 and the common electrodes 78 can be determined by the characteristic of the liquid crystal molecules. When the size of the pixel enlarges, the number of the pixel electrodes 76 and the number of common electrodes 78 in the pixel must increase. Therefore, the number of the disconnected common electrodes 78 increases, and the resistance of the common electrodes 78 will increase so that the interference will lower the quality of the screen in showing the picture.
All of the pixel electrodes 76 connect to the pads 70 via the through holes 74 on the second insulated layer. Sometimes, because one through hole 74 is formed defectively, the connection between the pixel electrode 76 and the pad 70 will be bad. Besides, when the first insulated layer has a broken hole during forming the Cs line 64, the voltage potential of the pixel electrode 76 will be the same as that of the Cs line 64. It cannot apply the predetermined voltage to all the pixel electrodes 76 of the pixel, and the whole pixel becomes defective.
As shown in FIG. 7, there are a plurality of through holes 74 on the second insulated layer and above the pads 70, and a plurality of pixel electrodes 76 connect to the pad 70 via the through holes 75 respectively to form the array substrate 61 of the in-plane-switching liquid crystal display. Even if one of the through holes 75 has defect, only the pixel electrode 76 connected to the defected through hole 74 becomes bad and the other pixel electrodes 76 can still work normally. However, when one of the pixel electrodes 76 change into high resistance characteristic, the angle of the AC current with square waveform flown to the pixel electrode 76 may become a circular shape and induce DC current component. After some time, the DC current may flow to the adjacent pixel electrode 76 by the alignment layer. After the liquid crystal display is used for a few hours, the voltage potentials of the two pixel electrodes 76 are the same so that the whole pixel cannot be switched.
Given the above, because the size of the pixel increases, various problems can easily occur. When a problem occurs, it will lower the quality of the liquid crystal display. Furthermore, the problem causes bad manufacturing yield of the liquid crystal display.
Prior art 1 discloses a liquid crystal display having large open ratio by decreasing a leakage electric field form the data line. A portion of the common electrode overlaps on the data line to prevent the leakage electric field. However, prior art 1 only discloses that the leakage electric field is shielded to enlarge the open ratio, and does not disclose that the defect caused by the large type pixel can be repaired. Prior art 1 is Japan Patent Publication No. 10-186407 (as shown in FIG. 1).